Seal assemblies for surgical access assemblies

ABSTRACT

Access assemblies includes an instrument valve housing and a valve assembly disposed within the cavity of the instrument valve housing. The valve assembly includes a guard assembly, and a seal assembly disposed distal of the guard assembly. In embodiments, the seal assembly includes a plurality of seal segments in an overlapping configuration. Each seal segment of the plurality of seal segments includes a seal portion having a smooth surface and a ribbed surface. The ribbed surfaces include a plurality of ribs extending in a radial direction.

FIELD

The present disclosure relates to surgical access assemblies for minimally invasive surgery. More particularly, the present disclosure relates to valve assemblies for surgical access assemblies.

BACKGROUND

In order to facilitate minimally invasive surgery, a working space must be created in a desired surgical site. An insufflation fluid, typically CO₂, is introduced into the abdomen of the patient to create an inflated state called a pneumoperitoneum. Surgical access assemblies are utilized to allow the introduction of surgical instrumentation and endoscopes (or other visualization tools). These surgical access assemblies maintain the pressure for the pneumoperitoneum, as they have one or more seals that adapt to the surgical instrumentation. Typically, a “zero-seal” in the surgical access assembly seals the surgical access assembly in the absence of a surgical instrument in the surgical access assembly, and an instrument seal seals around a surgical instrument that has been inserted through the surgical access assembly.

The breadth of surgical instrumentation on the market today requires a robust instrument seal capable adjusting to multiple sizes and withstanding multiple insertions and removals of surgical instrumentation. Some of the instrumentation can include sharp edges that can tear or otherwise damage instrument seals. Therefore, it would be beneficial to have a surgical access assembly with improved instrument seal durability.

SUMMARY

An access assembly includes an instrument valve housing, and a valve assembly disposed within the cavity of the instrument valve housing. The instrument valve housing including upper, lower, and inner housing sections and defining a cavity. The valve assembly includes a guard assembly, and a seal assembly disposed distal of the guard assembly. The seal assembly includes a plurality of seal segments in an overlapping configuration. Each seal segment of the plurality of seal segments includes a seal portion having a smooth surface and a ribbed surface. The ribbed surfaces include a plurality of ribs extending in a radial direction.

In embodiments, the seal assembly includes a ring portion and first, second, third and fourth seal segments. The first, second, third, and fourth seal segments may be secured to the ring portion by connector portions. The connector portions may be living hinges. The smooth surfaces of the first, second, third, and fourth seal segments may face distally. The ribbed surfaces of the first, second, third, and fourth seal segments may face proximally. The smooth surfaces and the ribbed surfaces may alternate. The first seal segment may include a tab to facilitate assembly of the seal assembly. The plurality of seal segments may form a non-continuous inner seal circumference. The valve assembly may further include a centering mechanism for biasing the valve assembly toward a center of the cavity of the instrument valve housing.

A valve assembly includes a guard assembly and a seal assembly disposed distal of the guard assembly. The seal assembly includes a plurality of seal segments in an overlapping configuration. Each seal segment of the plurality of seal segments may include a seal portion having a smooth surface and a ribbed surface. The ribbed surfaces may include a plurality of ribs extending in a radial direction.

In embodiments, the seal assembly includes a ring portion and first, second, third and fourth seal segments. The first, second, third, and fourth seal segments are secured to the ring portion by connector portions. The connector portions may be living hinges. The smooth surfaces of the first, second, third, and fourth seal segments may face in a distal direction. The ribbed surfaces of the first, second, third, and fourth seal segments may face in a proximal direction. The smooth surfaces and the ribbed surface may alternate. The first seal segment may include a tab to facilitate assembly of the seal assembly. The plurality of seal segments may form a non-continuous inner seal circumference.

A seal assembly includes a ring portion, and a plurality of seal segments extending from the ring portion in an overlapping configuration. Each seal segment of the plurality of seal segments includes a seal portion having a smooth surface and a ribbed surface. The ribbed surfaces may include a plurality of ribs extending in a radial direction.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and, together with a general description of the disclosure given above, and the detailed description of the embodiments given below, serve to explain the principles of the disclosure, wherein:

FIG. 1 is a side perspective view of a surgical access assembly according to an embodiment of the present disclosure;

FIG. 2 a side cross-sectional view of the surgical access assembly shown in FIG. 1 taken along section line 2-2;

FIG. 3 is an exploded perspective view of a valve assembly, with parts separated, including a centering mechanism, a guard assembly, a seal assembly, and a retainer assembly;

FIG. 4 is a top perspective view of the seal assembly shown in FIG. 3;

FIG. 5 is a perspective view of the seal assembly shown in FIG. 4, in an initial or unfolded condition;

FIG. 6 is a side cross-sectional view of the seal assembly shown in FIG. 4 taken along section line 6-6 in FIG. 9;

FIG. 7 is an enlarged view of the indicated area of detail shown in FIG. 6;

FIG. 8 is a side cross-sectional view of the seal assembly shown in FIG. 4 taken along section line 8-8 in FIG. 4;

FIG. 9 is a bottom perspective view of the seal assembly shown in FIG. 4, in the initial or unfolded condition;

FIG. 10 is a top perspective view of the seal assembly shown in FIG. 4, in a partially folded condition;

FIG. 11 is a top perspective view of the seal assembly shown in FIG. 4, in fully folded condition;

FIG. 12 is a bottom perspective view of the seal assembly shown in FIG. 3; and

FIG. 13 is a side cross-sectional view of the valve assembly shown in FIG. 3 taken along section line 13-13 in FIG. 12.

DETAILED DESCRIPTION

Particular embodiments of the present disclosure are described hereinbelow with reference to the accompanying drawings; however, it is to be understood that the disclosed embodiments are merely exemplary of the disclosure and may be embodied in various forms. Well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present disclosure in virtually any appropriately detailed structure. Like reference numerals refer to similar or identical elements throughout the description of the figures.

As used herein, the term “distal” refers to that portion of the instrument, or component thereof which is farther from the user while the term “proximal” refers to that portion of the instrument or component thereof which is closer to the user. As used herein, the term “about” means that the numerical value is approximate and small variations would not significantly affect the practice of the disclosed embodiments. Where a numerical limitation is used, unless indicated otherwise by the context, “about” means the numerical value can vary by ±10% and remain within the scope of the disclosed embodiments.

Surgical access assemblies with obturators are employed during minimally invasive surgery, e.g., laparoscopic surgery, and provide for the sealed access of surgical instruments into an insufflated body cavity, such as the abdominal cavity. The surgical access assemblies of the present disclosure include an instrument valve housing mounted on a cannula tube, and include an obturator (not shown) inserted through the valve housing and cannula. The obturator can have a blunt distal end, or a bladed or non-bladed penetrating distal end and can be used to incise the abdominal wall so that the surgical access assembly can be introduced into the abdomen. The handle of the obturator can engage or selectively lock into the instrument valve housing of the surgical access assembly.

Surgical access assemblies are employed to tunnel through an anatomical structure, e.g., the abdominal wall, either by making a new passage through the anatomical structure or by passing through an existing opening through the anatomical structure. Once the surgical access assembly with the obturator has tunneled through the anatomical structure, the obturator is removed, leaving the surgical access assembly in place. The instrument valve housing of the surgical access assembly includes valves that prevent the escape of insufflation fluid from the body cavity, while also allowing surgical instruments to be inserted into the body cavity.

In various embodiments, a bladeless optical trocar obturator may be provided that permits separation of tissue planes in a surgical procedure and visualization of body tissue fibers as they are being separated, thereby permitting a controlled traversal across a body wall. In other embodiments, the trocar obturator may be bladeless without being optical, e.g., without providing contemporaneous visualization thereof through the distal tip of an obturator. The bladeless obturator may be provided for the blunt dissection of the abdominal lining during a surgical procedure.

Various trocar obturators suitable for use with the surgical access assembly of the present disclosure are known and include, for example, bladed, bladeless, blunt, optical, and non-optical. For a detailed description of the structure and function of exemplary trocar assemblies, including exemplar trocar obturators and exemplar cannulas, please refer to PCT Publication No. WO 2016/186905 (“the '905 publication”), the content of which is hereby incorporated by reference herein in its entirety.

With initial reference now to FIG. 1, a surgical access assembly according to aspects of the present disclosure is shown generally as surgical access assembly 100. The surgical access assembly 100 includes a cannula 102 and an instrument valve housing 110 secured to the cannula 102. For a detailed description of an exemplary surgical access assembly, please refer to the '905 publication.

With reference to FIG. 2, the instrument valve housing 110 of the surgical access assembly 100 includes an upper housing section 112, a lower housing section 114, and an inner housing section 116. The upper, lower, and inner housing sections 112, 114, 116 are configured to support a valve assembly 120 on a proximal end of the cannula 102. More particularly, the inner housing section 116 is secured between the upper and lower housing sections 112, 114, and the valve assembly 120 is received between the inner and lower housing sections 116, 114. The upper and lower housing sections 112, 114 of the instrument valve housing 110 may be selectively attachable to, and detachable from, the inner housing section 116. The lower housing section 114 may be releasably or permanently attached to a cannula tube 104 (FIG. 1) of the cannula 102. In embodiments, either or both of the upper and lower housing sections 112, 114 of the instrument valve housing 110 may include knurls, indentations, tabs, or be otherwise configured to facilitate engagement by a clinician.

The surgical access assembly 100 may also include features for the stabilization of the surgical access assembly. For example, the distal end of the cannula tube 104 may carry a balloon anchor or another expandable member that engages the abdomen from the interior side. For example, see U.S. Pat. No. 7,300,448, the entire disclosure of which is hereby incorporated by reference herein. A feature on the opposite side of the abdominal wall may be used to further stabilize the surgical access assembly, such as adhesive tabs or adjustable foam collars.

The upper, lower, and inner housing sections 112, 114, 116 of the instrument valve housing 110 define a longitudinal passage 111 for receipt of a surgical instrument (not shown). The valve assembly 120 is supported within the instrument valve housing 110 to provide sealed passage of the surgical instrument (not shown) through the surgical access assembly 100.

With particular reference to FIGS. 2 and 3, the valve assembly 120 supported in the instrument valve housing 110 (FIG. 2) includes a centering mechanism 130, a guard assembly 140, a seal assembly 160, and a retainer assembly 190. The centering mechanism 130 of the valve assembly 120 permits radial movement of the valve assembly 120 relative to the instrument valve housing 110 when a surgical instrument is received through the valve assembly 120, and returns the valve assembly 120 to a generally centered position once the surgical instrument is withdrawn from within the instrument valve housing 110. The guard assembly 140 protects the seal assembly 160 during insertion and withdrawal of a surgical instrument through the seal assembly 160. The seal assembly 160 provides sealed passage of the surgical instrument through the instrument valve housing 110. The retainer assembly 190 maintains the centering mechanism 130, the guard assembly 140, and the seal assembly 160 in an aligned relationship with one another.

With continued reference to FIGS. 2 and 3, as noted above, the centering mechanism 130 of the valve assembly 120 is configured to maintain the valve assembly 120 centered within the instrument valve housing 110 (FIG. 2) in the absence of a surgical instrument passing through the valve assembly 120. In embodiments, and as shown, the centering mechanism 130 includes an outer annular ring 132, an inner annular ring 134, and a bellows 136 disposed between the outer annular ring 132 and the inner annular ring 134. As shown in FIG. 2, the outer annular ring 132 is received between the inner housing section 116 and the lower housing section 114 to retain the centering mechanism 130 within the instrument valve housing 110. The inner annular ring 134 supports the guard assembly 140. For a detailed description of the structure and function of an exemplary centering mechanism, please refer to U.S. Pat. No. 6,702,787, the content of which is incorporated herein by reference in its entirety.

Although shown including the centering mechanism 130 having bellows 136, the valve assembly 120 may include alternative centering mechanisms. For example, the centering mechanism may include an annular base and a plurality of spokes extending from the base, as described in U.S. Pat. App. Pub. No. 2015/0025477 (“the '477 publication”), the content of which is incorporated herein by reference in its entirety. It is envisioned that the centering mechanism may include multiple sets of spokes, as disclosed in the '477 publication.

With continued reference to FIGS. 2 and 3, the guard assembly 140 of the valve assembly 120 is configured to protect the seal assembly 160 as a surgical instrument (not shown) passes through the instrument valve housing 110 (FIG. 2).

The guard assembly 140 includes a ring portion 142 and first, second, third, and fourth petals 144, 146, 148, 150. The first, second, third, and fourth petals 144, 146, 148, 150 define an opening 141 therebetween to facilitate sealed passage of a surgical instrument (not shown) through the guard assembly 140. Although shown including six (4) petals, it is envisioned that the guard assembly may include any suitable number of petals, and the petals may include flap portions of any size or configuration. For exemplary guard assemblies, as well as other aspects of surgical access assemblies, please refer to U.S. Pat. Nos. 5,895,377 and 6,569,120 (“the '377 and '120 patents”), the entire disclosures of which are hereby incorporated by reference herein. For detailed description of the structure and function of other exemplary guard assemblies, please refer to commonly owned U.S. patent application Ser. Nos. ______, 16/238,823, and ______ (Atty. Docket No. 203-12169, 203-12267, and 203-12319), the entire disclosures of which are incorporated herein by reference in its entirety.

Referring to FIGS. 4-6, the seal assembly 160 of the valve assembly 120 is configured to provide a seal around an outer surface of a surgical instrument passing through the instrument valve housing 110 (FIG. 1). In embodiments, and as shown, the seal assembly 160 forms a conical seal body; however, it is envisioned that the aspects of the present disclosure may be modified for use with a flat seal body.

The seal assembly 160 includes first, second, third, and fourth seal segments 162, 164, 166, 168 each having a base or ring portion 172, 174, 176, 178, respectively, and a respective seal portion 182, 184, 186, 188 supported by the respective ring portion 172, 174, 176, 178. The first and second seal segments 162, 164, the second and third seal segments 164, 166, and the third and fourth seal segments 166, 168, are connected to one another by a connector portion 162 a, 164 a, 166 a, respectively. The connector portions 162 a, 164 a, 166 a may include a living hinge, or be otherwise configured to permit folding of the respective first, second, third, and fourth seal segments 162, 164, 166, 168 with respect to each other.

The seal portions 182, 184, 186, 188 of the respective first, second, third, and fourth seal segments 162, 164, 166, 168 of the seal assembly 160 are formed of an elastic material, e.g., rubber, and define a semi-conical configuration when the seal assembly 160 is in the folded condition. As noted above, the seal portions 182, 184, 186, 188 may alternatively define a flat seal. In embodiments, the seal portions 182, 184, 186, 188 are formed of polyurethane, polyisoprenes, or silicone elastomers. The ring portions 172, 174, 176, 178 of the respective first, second, third, and fourth seal segments 162, 164, 166, 168 of the seal assembly 160 may be formed of the same or different materials as the respective seal portions 182, 184, 186, 188. In embodiments, the seal portions 182, 184, 186, 188 may include one or more fabric layers.

The ring portions 172, 174, 176, 178 of the respective first, second, third, and fourth seal segments 162, 164, 166, 168 of the seal assembly 160 define openings 173, 175, 177, 179, respectively, and a plurality of openings 173 a, 175 a, 177 a, 179 a corresponding to a plurality of pins 196 (FIG. 13) extending from an upper retainer member 192 of the retainer assembly 190. In embodiments, and as shown, the ring portion 172 of the first seal section 162 may include a tab 172 a to facilitate assembly and/or positioning of the seal assembly 160.

The seal portions 182, 184, 186, 188 of the respective first, second, third, and fourth seal segments 162, 164, 166, 168 of the seal assembly 160 define a central opening 161 and are configured to receive a surgical instrument (not shown) through the valve assembly 120 in a sealed manner. The seal portions 182, 184, 186, 188, form a non-continuous or virtual seal circumference to reduce tearing during insertion, manipulation, and/or withdrawal of a surgical instrument (not shown) through the valve assembly 120.

An inner edge of the seal portions 182, 184, 186, 188 of the respective first, second, third, and fourth seal segments 162, 164, 166, 168 of the seal assembly 160 forms an angle “α” (FIG. 9) between about one-hundred eighty degrees (180°) and about two-hundred twenty degrees (220°). In this manner, each seal portion 182, 184, 186, 188 occupies at least fifty percent (50%) of the respective opening 173, 175, 177, 179 in the ring portions 172, 174, 176, 178, respectively.

With particular reference to FIGS. 5 and 9, the seal portions 182, 184, 186, 188 of the respective first, second, third, and fourth sections 162, 164, 166, 168 of the seal assembly 160 includes a first or ribbed surface 182 a, 184 a, 186 a, 188 a and a second or smooth surface 182 b, 184 b, 186 b, 188 b. When the seal assembly 160 is in a folded condition (FIG. 4), the ribbed surfaces 182 a, 184 a, 186 a, 188 a face proximally and the smooth surfaces 182 b, 184 b, 186 b, 188 b face distally. In this manner, the smooth surfaces 182 b, 184 b, 186 b of the respective seal portions 182, 184, 186 of the first, second and third seal segments 162, 164, 166, respectively, engage the ribbed surfaces 184 a, 186 a, 188 a of the respective seal portions 184, 186, 188 of the second, third, and fourth seal segments 164, 166, 168.

The ribbed surfaces 182 a, 184 a, 186 a, 188 a of the respective seal portions 182, 184, 186, 188 of the first, second, third, and fourth seal segments 162, 164, 166, 168, respectively, include a plurality of raised portions or ribs 183, 185, 187, 189. Each rib 183 a, 185 a, 187 a, 189 a of the plurality of ribs 183, 185, 187, 189 extends in a radial direction. In embodiments, and as shown in FIG. 7, each rib 183 a, 185 a, 187 a, 189 a is tapered on leading and trailing portions. Alternatively, each rib 183 a, 185 a, 187 a, 189 a may have only a leading or trailing tapered portion, or instead may include a consistent thickness.

The plurality of ribs 183, 185, 187, 189 of the ribbed surface 182 a, 184 a, 186 a, 188 a of the respective seal portions 182, 184, 186, 188 of the first, second, third, and fourth seal segments 162, 164, 166, 168, respectively, create extra padding along the ribbed surfaces 182 a, 184 a, 186 a, 188 a to reduce the likelihood of tearing the seal assembly during insertion, manipulation, and/or withdrawn of a surgical instrument (not shown) through the seal assembly 160. The plurality of ribs 183, 185, 187, 189 are arranged such then when the seal assembly 160 is in the folded condition (FIG. 4) the seal portions 182, 184, 186, 188 form a seal having a increased uniform thickness. The increased uniform thickness of the seal and/or the reinforcement provided by the plurality of ribs 183, 185, 187, 189 to the respective seal portions 182, 184, 186, 188 reduces the possibility of a surgical instrument (not shown) puncturing the seal portions 182, 184, 186, 188, thereby reducing the likelihood of tearing. This design also limits additional potential leak paths.

The method of folding the seal assembly 160 will now be described with reference to FIGS. 9-11. Referring initially to FIG. 9, the first seal section 162 of the seal assembly 160 is folded relative to the second seal section 164 of the seal assembly 160, as indicated by arrow “A”, such that the smooth surface 182 b (FIG. 5) of the first seal section 162 overlaps the ribbed surface 184 a (FIG. 5) of the second seal section 164. Similarly, the fourth seal section 168 of the seal assembly 160 is folded relative to the third seal section 166 of the seal assembly 160, as indicated by arrow “B”, such that the ribbed surface 188 a (FIG. 5) of the fourth section 168 overlaps the smooth surface 186 b (FIG. 5) of the third seal section 166.

Turning to FIG. 10, the first and second seal segments 162, 164 of the seal assembly 160 are then folded relative to the third and fourth seal segments 166, 168 of the seal assembly 160, as indicated by arrow “C”, such that the ribbed surface 184 a (FIG. 5) of the second seal section 164 overlaps the smooth surface 186 b (FIG. 5) of the third section 166.

With reference to FIGS. 12 and 13, the retainer assembly 190 (of the valve assembly 120) is configured to secure the guard assembly 140 relative to the seal assembly 160, and secure the guard and seal assemblies 140, 160 to the centering mechanism 130. The retainer assembly 190 includes an upper retainer member 192, and a lower retainer member 194.

As noted above, the upper retainer member 192 of the retainer assembly 190 includes a plurality of pins 196. The plurality of pins 196 extends from a bottom surface of the upper retainer member 192 (FIG. 13). Each pin 196 of the plurality of pins 196 is configured to be lockingly received within an opening 195 of a plurality of openings 195 of the lower retainer member 194. In embodiments, the plurality of pins 196 is welded, glued, adhered, bonded or otherwise secured within the plurality of openings 195 in the lower retainer member 194 to secure the upper retainer member 192 and the lower retainer member 194 together. Alternatively, the lower retainer member 194 may instead, or additionally, include a plurality of pins (not shown) with the upper retainer member 192 defining a plurality corresponding openings (not shown). Either or both of the upper and lower retainer members 192, 194 may include locking features (not shown) for engaging the plurality of pins and securing the upper retainer member 192 to the lower retainer member 194.

With continued reference to FIGS. 12 and 13, the plurality of pins 196 of the upper retainer member 192 extends through the ring portion 142 of the guard assembly 140, through the inner annular ring 134 of the centering mechanism 130, through the seal assembly 160, and into the plurality of openings 195 in the lower retainer member 194. As noted above, placing the guard assembly 140 proximal of the seal assembly 160 reduces or eliminates potential damage to the seal assembly 160 during insertion and retraction of a surgical instrument through the seal assembly 160. The placement of the guard assembly 140 also reduces the potential of the seal assembly 160 disintegrating into the body cavity during minimally invasive procedures.

During a surgical procedure utilizing surgical access assembly 100 (FIG. 1), a surgical instrument (not shown) is introduced into the instrument valve housing 110 through the longitudinal passage 111 in the upper, lower, and inner housing sections 112, 114, 116 (FIG. 2). As described in the '377 and '120 patents, the distal end of the surgical instrument engages the first, second, third, and fourth petals 144, 146, 148, 150 (FIG. 3) of the guard assembly 140 causing flaps of the respective first, second, third, and fourth petals 144, 146, 148, 150 to flex downward into contact with the seal assembly 160 to cause the central opening 161 of the seal assembly 160 to open to accommodate passage of the surgical instrument through the seal assembly 160. The guard assembly 140 minimizes damage to the seal assembly 160 during insertion of an instrument through the valve assembly 120

As noted above, the plurality of ribs 183, 185, 187, 189 of the ribbed surface 182 a, 184 a, 186 a, 188 a of the respective seal portions 182, 184, 186, 188 of the first, second, third, and fourth seal segments 162, 164, 166, 168, respectively, create extra padding along the ribbed surface 182 a, 184 a, 186 a, 188 a to reduce the likelihood of tearing the seal assembly during insertion, manipulation, and/or withdrawn of a surgical instrument (not shown) through the seal assembly 160.

While various embodiments of the present disclosure have been shown and described herein, it will be obvious to those skilled in the art that these embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the present disclosure. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims. 

What is claimed is:
 1. An access assembly comprising: an instrument valve housing including upper, lower, and inner housing sections and defining a cavity; and a valve assembly disposed within the cavity of the instrument valve housing, the valve assembly including: a guard assembly; and a seal assembly disposed distal of the guard assembly, the seal assembly including a plurality of seal segments in an overlapping configuration, each seal segment of the plurality of seal segments including a seal portion having a smooth surface and a ribbed surface, wherein the ribbed surfaces include a plurality of ribs extending in a radial direction.
 2. The access assembly of claim 1, wherein the seal assembly includes a ring portion and first, second, third and fourth seal segments.
 3. The access assembly of claim 2, wherein the first, second, third, and fourth seal segments are secured to the ring portion by connector portions.
 4. The access assembly of claim 3, wherein the connector portions are living hinges.
 5. The access assembly of claim 1, wherein the smooth surfaces of the first, second, third, and fourth seal segments face distally.
 6. The access assembly of claim 1, wherein the ribbed surfaces of the first, second, third, and fourth seal segments face proximally.
 7. The access assembly of claim 1, wherein the smooth surfaces and the ribbed surfaces alternate.
 8. The access assembly of claim 2, wherein the first seal segment includes a tab to facilitate assembly of the seal assembly.
 9. The access assembly of claim 1, wherein the plurality of seal segments form a non-continuous inner seal circumference.
 10. The access assembly of claim 1, further including a centering mechanism for biasing the valve assembly toward a center of the cavity of the instrument valve housing.
 11. A valve assembly comprising: a guard assembly; and a seal assembly disposed distal of the guard assembly, the seal assembly including a plurality of seal segments in an overlapping configuration, each seal segment of the plurality of seal segments including a seal portion having a smooth surface and a ribbed surface, wherein the ribbed surfaces include a plurality of ribs extending in a radial direction.
 12. The valve assembly of claim 11, wherein the seal assembly includes a ring portion and first, second, third and fourth seal segments.
 13. The valve assembly of claim 12, wherein the first, second, third, and fourth seal segments are secured to the ring portion by connector portions.
 14. The valve assembly of claim 13, wherein the connector portions are living hinges.
 15. The valve assembly of claim 11, wherein the smooth surfaces of the first, second, third, and fourth seal segments face in a distal direction.
 16. The valve assembly of claim 11, wherein the ribbed surfaces of the first, second, third, and fourth seal segments face in a proximal direction.
 17. The valve assembly of claim 11 wherein the smooth surfaces and the ribbed surface alternate.
 18. The valve assembly of claim 12, wherein the first seal segment includes a tab to facilitate assembly of the seal assembly.
 19. The valve assembly of claim 11, wherein the plurality of seal segments form a non-continuous inner seal circumference.
 20. A seal assembly comprising: a ring portion; and a plurality of seal segments extending from the ring portion in an overlapping configuration, each seal segment of the plurality of seal segments including a seal portion having a smooth surface and a ribbed surface, wherein the ribbed surfaces include a plurality of ribs extending in a radial direction. 